scripts/checkpatch: Fix typo in SPDX-License-Identifier keyword

scripts/checkpatch: Fix typo in SPDX-License-Identifier keyword

Fix the typo in the error message to help `grep` the example:

ERROR: New file '***' requires 'SPDX-License-Identifer'

Fixes: fa4d79c64dae ("scripts: mandate that new files have SPDX-License-Identifier")
Signed-off-by: Zhao Liu <zhao1.liu@intel.com>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Message-ID: <20250408162702.2350565-1-zhao1.liu@intel.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>